Differential Cold Tolerance of Quackgrass and Johnsongrass Rhizomes

Rhizomes of quackgrass [Agropyron repens(L.) Beauv.] and johnsongrass [Sorghum halepense(L.) Pers.] were buried at various depths in the soil in the fall of 1972 and 1973, then removed at different times for viability tests. Quackgrass rhizomes retained viability at 2 cm where the coldest temperatures were −17 C. Johnsongrass rhizomes survived the winter at depths of 20 cm or more, and were killed at temperatures below about −9 C. Quackgrass rhizomes had a higher concentration of lipids and higher proportions of unsaturated fatty acids than did johnsongrass rhizomes. This difference may contribute to the superior cold tolerance of the quackgrass rhizomes.